Controlling flow of black powder in hydrocarbon pipelines

ABSTRACT

Black powder flowing with hydrocarbons in a hydrocarbon pipeline is converted into a magnetorheological slurry by implementing wet scrubbing in the hydrocarbon pipeline. A flow of the magnetorheological slurry through the hydrocarbon pipeline is controlled.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of and claims the benefitof priority to U.S. application Ser. No. 15/597,619, filed on May 17,2017, which is a continuation of U.S. application Ser. No. 14/733,674,filed on Jun. 8, 2015, the contents of which are hereby incorporated byreference.

TECHNICAL FIELD

This specification relates to cleaning hydrocarbon pipelines, forexample, in situ hydrocarbon pipelines which are in service.

BACKGROUND

“Black powder” is a term used to describe the appearance of a materialthat is found in hydrocarbon pipelines (for example, natural gaspipelines) and other pipelines. The material is sometimes wet eitherfrom water or liquid hydrocarbons. The solids include a mechanicalmixture or chemical combinations of iron sulfides, iron oxides, dirt,sand, salts, chlorides, water, glycols, hydrocarbons, compressor oils,mill scale, or other materials. Black powder can be caused by bacterialand chemical corrosion of a carbon steel pipeline wall. Moisture can actas a catalyst that creates the corrosion resulting in production of ironsulfides and iron oxides in different forms. Black powder sometimesconsists of magnetite (iron oxide) and can also include components suchas manganese (Mn) and magnesium (Mg).

Black powder is a common problem affecting hydrocarbon pipelinesworld-wide. Black powder is an extremely hard abrasive material, whichcan cause erosion of the pipeline wall, seize valves, and damage meters.Black powder can also damage compressors and turbine components. Inliquid transmission pipelines, black powder can sometimes cause pumpfailure.

SUMMARY

This specification describes controlling the flow of black powder inhydrocarbon pipelines.

Some aspects of the subject matter described in this specification canbe implemented as a method. Black powder flowing with hydrocarbons in ahydrocarbon pipeline is converted into a magnetorheological slurry byimplementing wet scrubbing in the hydrocarbon pipeline. A flow of themagnetorheological slurry through the hydrocarbon pipeline iscontrolled.

This, and other aspects, can include one or more of the followingfeatures. To implement a wet scrubbing, the black powder can becoalesced into the magnetorheological slurry by mixing a quantity of acarrier fluid and a quantity of a thixotropic agent with thehydrocarbons in the hydrocarbon pipeline. The magnetorheological slurryincludes the carrier fluid, the thixotropic agent, and the black powder.To coalesce the black powder into the magnetorheological slurry, aquantity of surfactants can be mixed with the quantity of the carrierfluid and the quantity of the thixotropic agent. The quantity of thecarrier fluid and the quantity of the thixotropic agent can be mixedwith the hydrocarbons in the hydrocarbon pipeline using a turbulence ofthe hydrocarbons flowing in the hydrocarbon pipeline. The flow of themagnetorheological slurry through the hydrocarbon pipeline can becontrolled by removing the magnetorheological slurry from thehydrocarbon pipeline. The carrier fluid and the thixotropic agent can beseparated from the magnetorheological slurry, for example, afterremoving the magnetorheological slurry from the hydrocarbon pipeline. Tocontrol the flow of the magnetorheological slurry through thehydrocarbon pipeline, the hydrocarbons and the magnetorheological slurrycan be rotationally flowed through a vortex chamber connected to thehydrocarbon pipeline. The rotational flowing can separate thehydrocarbons and the magnetorheological slurry. The separatedhydrocarbons can be flowed through a first outlet of the vortex chamberin the hydrocarbon pipeline. The separated magnetorheological slurry canbe flowed through a second outlet of the vortex chamber. The blackpowder can include magnetic particles. A magnetic field can be appliedto the magnetorheological slurry to control the flow of themagnetorheological slurry through the hydrocarbon pipeline. The magneticfield can be generated by at least one of a permanent magnet, anelectromagnet, or a series of variable magnetic inductance coils. Theblack powder can include non-magnetic particles which are coalesced withthe magnetic particles in the magnetorheological slurry. Thehydrocarbons can include hydrocarbon gas. The black powder can includemicrometer-sized particles.

Some aspects of the subject matter described here are implemented as asystem that includes a wet scrubber system and a flow controller. Thewet scrubber system is configured to be connected to a hydrocarbonpipeline flowing hydrocarbons and black powder. The wet scrubber systemis configured to convert black powder flowing with hydrocarbons in thehydrocarbon pipeline into a magnetorheological slurry by implementing awet scrubbing in the hydrocarbon pipeline. The flow controller isconfigured to be connected to the hydrocarbon pipeline and to control aflow of the magnetorheological slurry through the hydrocarbon pipeline.

This, and other aspects, can include one or more of the followingfeatures. The flow controller can be configured to control the quantityof the carrier fluid and the quantity of the thixotropic agent to beflowed into the hydrocarbon pipeline. The quantity of the carrier fluidand the quantity of the thixotropic agent can be mixed with thehydrocarbons in the hydrocarbon pipeline utilizing a turbulence of thehydrocarbons flowing in the hydrocarbon pipeline. A vortex chamber canbe configured to receive the hydrocarbons and the magnetorheologicalslurry. The vortex chamber can be configured to be connected to thehydrocarbon pipeline to rotationally flow the hydrocarbons through thevortex chamber. The rotational flowing can separate the hydrocarbonsfrom the magnetorheological slurry. The vortex chamber can include afirst outlet through which the separated hydrocarbons are flowed intothe hydrocarbon pipeline and a second outlet through which the separatedmagnetorheological slurry is flowed. The black powder can includemagnetic particles. The flow controller can include a magnetic flowcontroller configured to apply a magnetic field to themagnetorheological slurry. The magnetic flow controller can include atleast one of a permanent magnet, an electromagnet, or a series ofvariable magnetic inductance coils.

The details of one or more implementations of the subject matterdescribed in this specification are set forth in the accompanyingdrawings and the description below. Other features, aspects, andadvantages of the subject matter will become apparent from thedescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an example of a system for controllinga flow of black powder in a hydrocarbon pipeline.

FIG. 2 is a schematic diagram of an example of a first implementation ofa system for controlling the flow of black powder in a hydrocarbonpipeline.

FIG. 3 is a schematic diagram of an example of a second implementationof a system for controlling the flow of black powder in a hydrocarbonpipeline.

FIG. 4 is a flowchart of an example of a process for controlling theflow of black powder in a hydrocarbon pipeline.

DETAILED DESCRIPTION

This specification describes controlling flow of black powder inhydrocarbon pipelines. For example, the subject matter described herecan be implemented to remove black powder from hydrocarbon pipelines insitu, that is, from hydrocarbon pipelines in the field that are inservice and that are actively transporting hydrocarbons such ashydrocarbon gas. One technique to clean pipelines by removing blackpowder is to filter the black powder at entrances of processing plantsor networks. However, the physical characteristics of black powder workagainst standard filtration. The particles in black powder can sheareasily at sub-micrometer sizes, allowing them to pass through gasseparation devices and filters configured to trap particles in thesub-micrometer size range. Consequently, filtration of black powder inflowing gas streams requires extra effort. In some instances, operatorsreplace or clean filter elements at optimum points shown by pressuredifferentials across the filters to minimize flow resistance, powderpenetration, or overfill. Filtering can also involve expensivereinforced filter elements to prevent the filter from collapsing underthe weight of the powder during gas flow.

Another technique to clean pipelines is to use water-based orhydrocarbon-based gels created by adding a gelling agent to a baseliquid to achieve higher viscosity of the liquid batch. Gels can be usedin pipeline cleaning operations to keep particles floating (insuspension). Doing so can enhance the displacement capabilities ofliquids. Due to the high viscosity, however, the gels may leave residuein the pipeline after cleaning. A gel breaker may be needed to removethe residue. Pipelines in service may, consequently, need large amountsof gel, making the application of gels problematic. In addition, gelshave lower wetting capability compared to other liquids due to changedsurface tension properties.

A further technique to clean pipelines is by chemical dissolution.However, chemical dissolution may not be viable to clean pipelines inservice because the chemical reactions require long contact times, whichis difficult to achieve while the cleaning pipelines are in service. Oneoption of chemical dissolution of black powder involves using chelants,which have shown good results on iron sulfide under laboratoryexperiments. However, large amounts of liquids are needed forapplications in pipelines. Moreover, chelants are water-based and cancorrode the pipelines, thereby becoming a part of the problem instead ofthe solution even when adding corrosion inhibitors.

This specification describes a technique to trap and to remove blackpowder flowing through a hydrocarbon pipeline. Black powder includesseveral forms of strongly magnetic material including mill scale,magnetite (Fe₃O₄), and greigite (Fe₃S₄). Black powder also includesnon-magnetic materials. Industry literature reports that black powderforms can range from weakly magnetic to strongly magnetic in nature.This specification describes techniques to convert black powder flowingwith hydrocarbons (for example, hydrocarbon gas) in a hydrocarbonpipeline to a carrier fluid using thixotropic agents, thereby creating amagnetorheological slurry. A magnetorheological fluid is a fluid thatchanges the way it flows in the presence of a magnetic field and becomesdirectable by applying a magnetic field to control a flow of themagnetorheological fluid away from (for example, out of) the hydrocarbonpipeline. These magnetorheological fluids can be in the form of liquidand aerosolized phases traveling in the hydrocarbon stream.

The subject matter described here can be implemented in thetechnological fields of natural gas processing, pipeline transportation,and natural gas measurement and operations, to name a few. Byimplementing the techniques described here, a concentration of blackpowder in a hydrocarbon pipeline can be decreased or eliminated.Consequently, the harmful effects of black powder on the hydrocarbonpipeline can be negated. In this manner, the techniques described herecan be implemented to solve a chronic hydrocarbon pipeline industryproblem. In addition, the black powder that is removed from thehydrocarbon pipeline can be recovered, processed, and used asferrofluids.

Ferrofluids find applications in several industries. Ferrofluids areoften used as rotating shaft seals in magnetic tapes, magneto-opticaldrives, ad rigid, and floppy disks. Ferrofluids are also used in audioloudspeakers to produce improved quality and higher manufacturingyields. Ferrofluids also find application in the biomedical field aspolymer microspheres that can be coated with antibodies ortherapeutic/chemotherapy drugs. Ferrofluids are also used in sensors,switches, and solenoids to improve performance in applications that useinclinometers, accelerometers, flow meters, pressure and level sensors,and various switches. Ferrofluids are also used in electricaltransformers to improve cooling by enhancing fluid circulation withintransformer windings.

Such fluids are specialty products whose production incurs highmanufacturing costs. Magnetic black powder, on the other hand, isautomatically generated in the hydrocarbon pipeline. Thus, using theblack powder recovered by implementing the techniques described here andprocessed to uniform particle sizes for use as ferrofluids in processesof other industries can decrease the costs associated with the processesof the other industries.

FIG. 1 is a schematic diagram of an example of a system for controllinga flow of black powder in a hydrocarbon pipeline 100. The hydrocarbonpipeline 100 can be an in situ pipeline in service. That is, thehydrocarbon pipeline 100 can be operational to transport hydrocarbons102 between locations. The hydrocarbons 102 can include hydrocarbon gas.In some instances, the hydrocarbons 102 can contain aerosolized aqueousor hydrocarbon liquids traveling in the pipeline 100 or separatedaqueous/hydrocarbon liquids traveling along walls of the pipeline 100.Black powder 104 is disbursed throughout and can flow with thehydrocarbons 102. The black powder 104 includes magnetic particles (forexample, magnetic particles 106 a) and non-magnetic particles (forexample, non-magnetic particles 106 b), as described above. Theparticles in the black powder 104 can have sizes in the range ofsubstantially one micrometer or less and can be dispersed in thehydrocarbon stream gas phase and liquid phases as solid particles. Ingeneral, the black powder 104 is small enough to be easily dispersed inthe hydrocarbons 102.

The system can include a wet scrubber system 108 configured to beconnected to the hydrocarbon pipeline 100. The wet scrubber system 100can be configured to convert the black powder 104 into amagnetorheological slurry 110 by binding black powder particles via acarrier liquid and thixotropic media. The magnetorheological slurry 110can contain black powder 104 entrained from the wet scrubbing processwhich includes magnetic particles 106 a, non-magnetic particles 106 b,and carrier and thixotropic liquids (described below). The wet scrubbingprocess serves to provide a preliminary removal process and serves as adistribution mechanism for binding the magnetic and non-magneticparticles by the liquid media. This binding process allows additionalmass for inertial removal for non-magnetic particles 106 b from the gasstream and also allows an increased separation effect for magneticparticles 106 a when a magnetic field is created from induction coils115 located along the pipeline surface. Movement of themagnetorheological slurry 110 can be managed through a systemcontrolling the timing and strength of the magnetic flux created by theinduction coils 115. Even small quantities of magnetic particlesdistributed through the magnetorheological slurry 110 can allow controlof flow of the non-magnetic particles 106 b, now part of themagnetorheological slurry 110 along the pipeline walls throughadditional magnetic induction coils 116, out of the pipeline system 114.

The system also includes a flow controller 112 configured to beconnected to the hydrocarbon pipeline 100. The flow controller 112 isconfigured to control the fluid distribution of the wet scrubbingprocess. In some implementations, the wet scrubber system 108 caninclude multiple storage tanks (described below), each storing acomponent to be mixed with the black powder 104 inside the hydrocarbonpipeline 100 to convert the black powder 104 into the magnetorheologicalslurry 110. The flow controller 112 can be connected to the wet scrubbersystem 108 to control a quantity of each component to be flowed into thehydrocarbon pipeline 100 and to flow the quantity into the hydrocarbonpipeline 100.

The flow controller 112 can be implemented as hardware, software,firmware, or combinations of them. In some implementations, the flowcontroller 112 can include a computer system including one or moreprocessors and a computer-readable medium storing instructionsexecutable by the one or more processors to perform operations. Inaddition, the flow controller 112 can include one or more pumps, one ormore valves or other flow control equipment (or combinations of them)connected to the computer system. The operations that the flowcontroller 112 can perform can include, for example, identifying aquantity of a component (such as a carrier fluid, a thixotropic agent,or other component), and operating the one or more pumps, the one ormore valves, or other flow control equipment to pump the identifiedquantity into the hydrocarbon pipeline 100.

As described above, the magnetorheological slurry 110 can be weaklymagnetic, strongly magnetic, or somewhere in between. In someimplementations, the magnetic flow controller 114 can be configured tocoordinate timing and strength of the magnetic field created by theinduction coils 115 or 116 to control a flow of the magnetorheologicalslurry 110, for example, away from the hydrocarbon pipeline 100. Someimplementations of the wet scrubber system and the flow controller willbe described below with reference to FIGS. 2 and 3.

FIG. 2 is a schematic diagram of an example of a first implementation ofa system for controlling the flow of black powder 204 in a hydrocarbonpipeline 200 flowing hydrocarbons 202, for example, hydrocarbon gas. Thehydrocarbon pipeline 200 is an in situ pipeline in service, that is, thepipeline 200 is implemented in the field and is transporting thehydrocarbons between locations. The wet scrubber system 208 can includemultiple storage tanks. For example, the storage tanks can include acarrier fluid storage tank 230 a configured to store a carrier fluid 232and to be connected to the hydrocarbon pipeline 200. The storage tankscan include a thixotropic agent storage tank 230 b configured to store athixotropic agent 234 and to be connected to the hydrocarbon pipeline200.

The system can include a flow controller 212 configured to be connectedto the hydrocarbon pipeline 200 and to the wet scrubber system 208. Theflow controller 212 can be substantially similar to the flow controller112 described above. In some implementations, the flow controller 212can be configured to control the quantity of the carrier fluid 232 andthe quantity of the thixotropic agent 234 flowed from the carrier fluidstorage tank 230 a and the thixotropic agent storage tank 230 b,respectively, into the hydrocarbon pipeline 200.

In some implementations, the storage tanks can include a surfactantstorage tank 230 c configured to store surfactants 236 and to beconnected to the hydrocarbon pipeline 200. Surfactants (sometimes calledsurface active agents) can be added to a batch of liquids, for example,hydrocarbon-based or water-based liquids, to create an efficient andtime-effective cleaning solution. Instead of attempting to dissolvecontaminants or trying to keep contaminants in solution, surfactantswill penetrate contaminants and break them up into pieces in a shorttime (for example, a reaction time as low as one minute). In thisdisclosure, surfactants serve as dispersion agents for magneticparticles in the carrier liquid that allow a stabilized magnetizedcolloidal suspension which can be displaced out of the hydrocarbonpipeline 200. The surfactants also serve as an enhanced scrubbing mediaby ensuring maximum contact area is available for black powder coating.The use of surfactants also significantly reduces the amount of carrierfluids required for the system and reduces the amount of free liquid tobe removed. The flow controller 212 can be configured to control thequantity of the surfactants 236 flowed from the surfactant storage tank230 c into the hydrocarbon pipeline 200.

In operation, the flow controller 212 can cause the wet scrubber system208 to implement a wet scrubbing to convert the black powder 204 into amagnetorheological slurry 210. To do so, the flow controller 212 cancause the wet scrubber system 208 to flow the quantity of the carrierfluid 232 and the quantity of the thixotropic agent 234 (and, in someimplementations, the quantity of the surfactants 236) into thehydrocarbon pipeline 200. The wet scrubber system 208 or the flowcontroller 212 can include tubing that is connected to the storage tanksand inserted into the hydrocarbon pipeline 200. An end of the tubinginserted into the hydrocarbon pipeline 200 can face the oncoming streamof hydrocarbons 202 and black powder 204.

When the quantity of the carrier fluid 232 and the quantity of thethixotropic agent 234 (and, in some implementations, the quantity of thesurfactants 236) are flowed into the hydrocarbon pipeline 200, thecomponents mix with the black powder 204 under the turbulence of thehydrocarbons 202 flowing in the hydrocarbon pipeline 200 resulting inthe magnetorheological slurry 210. In this manner, the black powder 204in the hydrocarbon pipeline 200 is converted into the magnetorheologicalslurry 210.

To remove the magnetorheological slurry 210 from the hydrocarbonpipeline 200, the system can include a vortex chamber 250 configured toreceive the hydrocarbons 202 and the magnetorheological slurry 210. Thevortex chamber 250 can be connected to the hydrocarbon pipeline 200 insuch a manner that a rotational flow is induced in the hydrocarbons 202and the magnetorheological slurry 210 as the two fluids flow through thevortex chamber 250. Such a rotational flow can be induced by anarrangement of the vortex chamber 250 relative to the hydrocarbonpipeline 200. The vortex chamber 250 can be connected in series with orin parallel with the hydrocarbon pipeline 200.

In some implementations, a bend 252 can be introduced in the hydrocarbonpipeline 200 downstream of the location at which the black powder 204 isconverted into the magnetorheological slurry 210. The vortex chamber 250can have a cylindrical cross-section. The vortex chamber 250 can includean inlet 254 formed at an outer circumference of the vortex chamber 250and offset from a longitudinal axis of the vortex chamber 250. Thehydrocarbon pipeline 200 at the bend 252 can be connected to the inlet254 such that the hydrocarbons 202 and the magnetorheological slurry 210flow almost tangentially to an inner surface of the vortex chamber 250,thereby rotating as the hydrocarbons 202 and the magnetorheologicalslurry 210 flow through the vortex chamber 250.

Because the hydrocarbons 202 and the magnetorheological slurry 210 arein two different phases, as a preliminary separation, the rotationalflow can create a centrifugation action forcing the magnetorheologicalslurry 210 to the inner walls of the vortex chamber 250 while thehydrocarbons 202, which are relatively unaffected by the centrifugationaction, remain nearer to the center of the vortex chamber 250. In thismanner, the hydrocarbons 202 and the magnetorheological slurry 210 canbe separated. The vortex chamber 250 can include a first outlet 256through which the separated hydrocarbons can be flowed into anothersection of the hydrocarbon pipeline (not shown). The vortex chamber 250can include a second outlet 258 through which the separatedmagnetorheological slurry 210 can be flowed, as described below.

In some implementations, the system can include a magnetic flowcontroller 214 connected to the vortex chamber 250 (for example, to anouter circumference of the vortex chamber 250) to separate themagnetorheological slurry 210 from the hydrocarbons 202. The magneticflow controller 214 can be implemented as at least one of a permanentmagnet, an electromagnet, a series of variable magnetic inductancecoils, or a combination of them. The magnetic flow controller 214 can beconfigured to generate a variable magnetic field that can be controlledusing the flow controller 212. By applying the magnetic field (forexample, magnetic induction), the magnetic magnetorheological slurry 210can be moved along the inner side walls of the vortex chamber 250towards the second outlet 258 through which the separatedmagnetorheological slurry 210 can be flowed.

In some implementations, the vortex chamber 250 can include a filter 260(for example, an electrostatic screen). The filter 260 can be placednear the first outlet 256 and can be configured to capture anyaerosolized magnetorheological slurry 210 that did not get separated inthe vortex chamber 250.

In some implementations, multiple systems such as those described abovewith reference to FIG. 2 can be connected at corresponding multiplelocations along the hydrocarbon pipeline 200. Black powder flow controland separation can be implemented using one or more of the multiplesystems. In such implementations, a maintenance, repair, or replacementof at least one of the systems can be performed while at least anotherof the systems simultaneously separates the black powder 204 from thehydrocarbons 202 in the hydrocarbon pipeline 200.

FIG. 3 is a schematic diagram of an example of a second implementationof a system for controlling the flow of black powder 304 in ahydrocarbon pipeline 300. The hydrocarbon pipeline 300 is in situ, thatis, the pipeline is implemented in the field and is in service totransport the hydrocarbons between locations. The wet scrubber system308 can include multiple storage tanks. For example, the storage tankscan include a carrier fluid storage tank 330 a configured to store acarrier fluid 332 and to be connected to the hydrocarbon pipeline 300.The storage tanks can include a thixotropic agent storage tank 330 bconfigured to store a thixotropic agent 234 and to be connected to thehydrocarbon pipeline 300.

The system can include a flow controller 312 configured to be connectedto the hydrocarbon pipeline 300 and to the wet scrubber system 308. Theflow controller 312 can be substantially similar to the flow controller112 described above. In some implementations, the flow controller 312can be configured to control the quantity of the carrier fluid 332 andthe quantity of the thixotropic agent 334 flowed from the carrier fluidstorage tank 330 a and the thixotropic agent storage tank 330 b,respectively, into the hydrocarbon pipeline 300. In someimplementations, the storage tanks can include a surfactant storage tank330 c configured to store surfactants 336 and to be connected to thehydrocarbon pipeline 300. The flow controller 312 can be configured tocontrol the quantity of the surfactants 336 flowed from the surfactantstorage tank 330 c into the hydrocarbon pipeline 300.

In operation, the flow controller 312 can cause the wet scrubber system308 to implement a wet scrubbing to convert the black powder 304 into amagnetorheological slurry 310. To do so, the flow controller 312 cancause the wet scrubber system 308 to flow the quantity of the carrierfluid 332 and the quantity of the thixotropic agent 334 (and, in someimplementations, the quantity of the surfactants 336) into thehydrocarbon pipeline 300. The wet scrubber system 308 or the flowcontroller 312 can include tubing that is connected to the storage tanksand inserted into the hydrocarbon pipeline 300 through an inlet 362. Anend of the tubing inserted into the hydrocarbon pipeline 300 can beconnected to multiple sprayers (for example, a first sprayer 360 a, asecond sprayer 360 b, a third sprayer 360 c, a fourth sprayer 360 c, andmore or fewer sprayers), that can spray the components received from thestorage tanks onto the hydrocarbons 300 and the black powder 304 tocreate a foam zone 356.

When the quantity of the carrier fluid 332 and the quantity of thethixotropic agent 334 (and, in some implementations, the quantity of thesurfactants 336) are sprayed on to the hydrocarbons 302 and the blackpowder 304 in the hydrocarbon pipeline 300, the components mix with theblack powder 304 under the turbulence of the hydrocarbons 302 flowing inthe hydrocarbon pipeline 300 and under the turbulence created by thesprayers. Such mixing results in the magnetorheological slurry 310 beingformed in the foam zone 356. In this manner, the black powder 304 in thehydrocarbon pipeline 300 is converted into the magnetorheological slurry310.

In some implementations, the system can include a magnetic flowcontroller 314 connected to the hydrocarbon pipeline 300 to separate themagnetorheological slurry 310 from the hydrocarbons 302. The magneticflow controller 314 can be implemented as at least one of a permanentmagnet, an electromagnet, a series of variable magnetic inductancecoils, or a combination of them. The magnetic flow controller 314 can beconfigured to generate a variable magnetic field that can be controlledusing the flow controller 312

In use, an outlet 364 can be formed in the hydrocarbon pipeline 300 tocollect the magnetorheological slurry 310 formed in the foam zone 356.In some implementations, the inlet 362 and the outlet 364 can be formedon a circumferential surface of the hydrocarbon pipeline 300 atdiametrically opposite locations. In some implementations, the outlet364 can be formed at any location on the circumferential surfacedownstream of the inlet 362. The magnetic flow controller 314 can beconnected to the hydrocarbon pipeline 300 around the outlet 364 and canapply a magnetic field to remove the magnetorheological slurry 310 outof the hydrocarbon pipeline 300 through the outlet 364. For example, byapplying the magnetic field (for example, magnetic induction), themagnetic magnetorheological slurry 310 can be attracted toward theoutlet 364. Alternatively or in addition, the magnetorheological slurry310 can be moved along the inner side walls of the hydrocarbon pipeline300 near the outlet 364 and directed towards the outlet 364

In some implementations, multiple systems such as those described abovewith reference to FIG. 3 can be connected at corresponding multiplelocations along the hydrocarbon pipeline 300. Black powder flow controland separation can be implemented using one or more of the multiplesystems. In such implementations, a maintenance, repair, or replacementof at least one of the systems can be performed while at least anotherof the systems simultaneously separates the black powder 304 from thehydrocarbons 302 in the hydrocarbon pipeline 300. Also, in someimplementations, some systems such as those described above withreference to FIG. 2 can be used in combination with systems such asthose described above with reference to FIG. 3.

FIG. 4 is a flowchart of an example of a process 400 for controlling theflow of black powder in a hydrocarbon pipeline. The hydrocarbon pipelinecan be an in situ pipeline in service. At 402, a carrier fluid and athixotropic agent (and, in some implementations, a surfactant) can bemixed with black powder flowing with hydrocarbons in the hydrocarbonpipeline. At 404, a flow of a resulting magnetorheological slurry can becontrolled. At 406, the magnetorheological slurry can be flowed out ofthe hydrocarbon pipeline by applying a magnetic field.

In the implementations described here, the components introduced intothe hydrocarbon pipeline to convert the black powder into themagnetorheological slurry (for example, the carrier fluid, thethixotropic agent, the surfactant) can be removed from the hydrocarbonpipeline with the black powder. The black powder can then be separatedfrom the components. To do so, in some implementations, a settlementtank with an inductance plate can be used. The separated components canthen be recirculated to the respective storage tanks for re-use. Theblack powder can be collected, processed, and used, for example, inapplications that use micron or sub-micron sized magnetic particles. Insuch instances, the magnetic and non-magnetic particles can be separatedbefore using the magnetic particles, for example, as ferrofluids.

Thus, particular implementations of the subject matter have beendescribed. Other implementations are within the scope of the followingclaims.

The invention claimed is:
 1. A method comprising: converting blackpowder flowing with hydrocarbons in a hydrocarbon pipeline into amagnetorheological slurry by implementing wet scrubbing in thehydrocarbon pipeline, wherein the black powder comprises magneticparticles; separating the magnetorheological slurry from thehydrocarbons resulting in separated magnetorheological slurry andseparated hydrocarbons; and flowing the separated magnetorheologicalslurry out of the hydrocarbon pipeline by applying a magnetic field tothe separated magnetorheological slurry.
 2. The method of claim 1,wherein the hydrocarbons comprise hydrocarbon gas.
 3. The method ofclaim 1, wherein the black powder comprise micrometer-sized particles.4. The method of claim 1, wherein flowing the separatedmagnetorheological slurry out of the hydrocarbon pipeline by applyingthe magnetic field to the separated magnetorheological slurry comprisesmoving the separated magnetorheological slurry along an inner side wallof the hydrocarbon pipeline towards an outlet of the hydrocarbonpipeline.
 5. The method of claim 1, wherein separating themagnetorheological slurry from the hydrocarbons resulting in separatedmagnetorheological slurry and separated hydrocarbons comprisesrotationally flowing the hydrocarbons and the magnetorheological slurrythrough a vortex chamber connected to the hydrocarbon pipeline.
 6. Themethod of claim 5, further comprising: flowing the separatedhydrocarbons through a first outlet of the vortex chamber into thehydrocarbon pipeline; and flowing the separated magnetorheologicalslurry through a second outlet of the vortex chamber.
 7. The method ofclaim 1, wherein the magnetic field is generated by at least one of apermanent magnet, an electromagnet, or a series of variable magneticinductance coils.
 8. The method of claim 7, wherein the black powdercomprises non-magnetic particles which are coalesced with the magneticparticles in the magnetorheological slurry.
 9. The method of claim 1,wherein implementing wet scrubbing comprises coalescing the black powderinto the magnetorheological slurry by mixing a quantity of a carrierfluid and a quantity of a thixotropic agent with the hydrocarbons in thehydrocarbon pipeline, wherein the magnetorheological slurry comprisesthe carrier fluid, the thixotropic agent, and the black powder.
 10. Themethod of claim 9, wherein coalescing the black powder into themagnetorheological slurry further comprises mixing a quantity ofsurfactants with the quantity of the carrier fluid and the quantity ofthe thixotropic agent.
 11. The method of claim 9, wherein the quantityof the carrier fluid and the quantity of the thixotropic agent are mixedwith the hydrocarbons in the hydrocarbon pipeline utilizing a turbulenceof the hydrocarbons flowing in the hydrocarbon pipeline.
 12. The methodof claim 11, further comprising separating the carrier fluid and thethixotropic agent from the separated magnetorheological slurry.